Solutions & Explanations

Browse 4,029+ detailed solutions with multiple approaches, code in Python, Java, C++ and more.

4,029 Solutions961 Easy2102 Medium966 Hard

Title	Difficulty	Acceptance	Topics	Solution
564. Find the Closest Palindrome	Hard	31.6%	Math String	Read
568. Maximum Vacation Days	Hard	46.7%	Array Dynamic Programming+1	Read
569. Median Employee Salary	Hard	65.9%	Database	Read
571. Find Median Given Frequency of Numbers	Hard	42.4%	Database	Read
579. Find Cumulative Salary of an Employee	Hard	47.8%	Database	Read
587. Erect the Fence	Hard	53.4%	Array Geometry+1	Read
588. Design In-Memory File System	Hard	48.0%	Design Hash Table+3	Read
591. Tag Validator	Hard	41.7%	Stack String	Read
600. Non-negative Integers without Consecutive Ones	Hard	43.1%	Dynamic Programming	Read
601. Human Traffic of Stadium	Hard	49.1%	Database	Read
615. Average Salary: Departments VS Company	Hard	56.2%	Database	Read
618. Students Report By Geography	Hard	63.5%	Database	Read
629. K Inverse Pairs Array	Hard	49.2%	Dynamic Programming	Read
630. Course Schedule III	Hard	42.1%	Array Greedy+2	Read
631. Design Excel Sum Formula	Hard	39.9%	Array Design+3	Read
632. Smallest Range Covering Elements from K Lists	Hard	70.3%	Array Greedy+4	Read
639. Decode Ways II	Hard	31.8%	Dynamic Programming String	Read
642. Design Search Autocomplete System	Hard	49.9%	Data Stream Depth-First Search+5	Read
644. Maximum Average Subarray II	Hard	37.7%	Array Binary Search+1	Read
656. Coin Path	Hard	34.2%	Array Dynamic Programming	Read
660. Remove 9	Hard	57.3%	Math	Read
664. Strange Printer	Hard	61.0%	Dynamic Programming String	Read
668. Kth Smallest Number in Multiplication Table	Hard	55.1%	Binary Search Math	Read
675. Cut Off Trees for Golf Event	Hard	36.8%	Array Breadth-First Search+2	Read
679. 24 Game	Hard	59.4%	Array Backtracking+1	Read
683. K Empty Slots	Hard	38.0%	Array Binary Indexed Tree+6	Read
685. Redundant Connection II	Hard	36.6%	Breadth-First Search Depth-First Search+2	Read
689. Maximum Sum of 3 Non-Overlapping Subarrays	Hard	59.8%	Array Dynamic Programming	Read
691. Stickers to Spell Word	Hard	50.7%	Array Backtracking+4	Read
699. Falling Squares	Hard	48.3%	Array Ordered Set+1	Read
710. Random Pick with Blacklist	Hard	35.4%	Array Binary Search+4	Read
711. Number of Distinct Islands II	Hard	55.3%	Breadth-First Search Depth-First Search+3	Read
715. Range Module	Hard	45.4%	Design Ordered Set+1	Read
716. Max Stack	Hard	45.9%	Design Doubly-Linked List+3	Read
719. Find K-th Smallest Pair Distance	Hard	46.4%	Array Binary Search+2	Read
726. Number of Atoms	Hard	65.1%	Hash Table Sorting+2	Read
727. Minimum Window Subsequence	Hard	43.5%	Dynamic Programming Sliding Window+1	Read
730. Count Different Palindromic Subsequences	Hard	48.2%	Dynamic Programming String	Read
732. My Calendar III	Hard	71.9%	Binary Search Design+3	Read
736. Parse Lisp Expression	Hard	53.5%	Hash Table Recursion+2	Read
741. Cherry Pickup	Hard	40.4%	Array Dynamic Programming+1	Read
745. Prefix and Suffix Search	Hard	41.2%	Array Design+3	Read
749. Contain Virus	Hard	55.9%	Array Breadth-First Search+3	Read
753. Cracking the Safe	Hard	58.5%	Depth-First Search Eulerian Circuit+1	Read
757. Set Intersection Size At Least Two	Hard	58.0%	Array Greedy+1	Read
759. Employee Free Time	Hard	72.9%	Array Heap (Priority Queue)+1	Read
761. Special Binary String	Hard	79.4%	Recursion String	Read
765. Couples Holding Hands	Hard	59.8%	Breadth-First Search Depth-First Search+3	Read
768. Max Chunks To Make Sorted II	Hard	54.7%	Array Greedy+3	Read
770. Basic Calculator IV	Hard	49.8%	Hash Table Math+3	Read

#564Hard

Find the Closest Palindrome

MathString

Acceptance: 31.6%

#568Hard

Maximum Vacation Days

ArrayDynamic ProgrammingMatrix

Acceptance: 46.7%

#569Hard

Median Employee Salary

Database

Acceptance: 65.9%

#571Hard

Find Median Given Frequency of Numbers

Database

Acceptance: 42.4%

#579Hard

Find Cumulative Salary of an Employee

Database

Acceptance: 47.8%

#587Hard

Erect the Fence

ArrayGeometryMath

Acceptance: 53.4%

#588Hard

Design In-Memory File System

DesignHash TableSorting+2

Acceptance: 48.0%

#591Hard

Tag Validator

StackString

Acceptance: 41.7%

#600Hard

Non-negative Integers without Consecutive Ones

Dynamic Programming

Acceptance: 43.1%

#601Hard

Human Traffic of Stadium

Database

Acceptance: 49.1%

#615Hard

Average Salary: Departments VS Company

Database

Acceptance: 56.2%

#618Hard

Students Report By Geography

Database

Acceptance: 63.5%

#629Hard

K Inverse Pairs Array

Dynamic Programming

Acceptance: 49.2%

#630Hard

Course Schedule III

ArrayGreedyHeap (Priority Queue)+1

Acceptance: 42.1%

#631Hard

Design Excel Sum Formula

ArrayDesignGraph+2

Acceptance: 39.9%

#632Hard

Smallest Range Covering Elements from K Lists

ArrayGreedyHash Table+3

Acceptance: 70.3%

#639Hard

Decode Ways II

Dynamic ProgrammingString

Acceptance: 31.8%

#642Hard

Design Search Autocomplete System

Data StreamDepth-First SearchDesign+4

Acceptance: 49.9%

#644Hard

Maximum Average Subarray II

ArrayBinary SearchPrefix Sum

Acceptance: 37.7%

#656Hard

Coin Path

ArrayDynamic Programming

Acceptance: 34.2%

#660Hard

Remove 9

Math

Acceptance: 57.3%

#664Hard

Strange Printer

Dynamic ProgrammingString

Acceptance: 61.0%

#668Hard

Kth Smallest Number in Multiplication Table

Binary SearchMath

Acceptance: 55.1%

#675Hard

Cut Off Trees for Golf Event

ArrayBreadth-First SearchHeap (Priority Queue)+1

Acceptance: 36.8%

#679Hard

24 Game

ArrayBacktrackingMath

Acceptance: 59.4%

#683Hard

K Empty Slots

ArrayBinary Indexed TreeHeap (Priority Queue)+5

Acceptance: 38.0%

#685Hard

Redundant Connection II

Breadth-First SearchDepth-First SearchGraph+1

Acceptance: 36.6%

#689Hard

Maximum Sum of 3 Non-Overlapping Subarrays

ArrayDynamic Programming

Acceptance: 59.8%

#691Hard

Stickers to Spell Word

ArrayBacktrackingBit Manipulation+3

Acceptance: 50.7%

#699Hard

Falling Squares

ArrayOrdered SetSegment Tree

Acceptance: 48.3%

#710Hard

Random Pick with Blacklist

ArrayBinary SearchHash Table+3

Acceptance: 35.4%

#711Hard

Number of Distinct Islands II

Breadth-First SearchDepth-First SearchHash Function+2

Acceptance: 55.3%

#715Hard

Range Module

DesignOrdered SetSegment Tree

Acceptance: 45.4%

#716Hard

Max Stack

DesignDoubly-Linked ListLinked List+2

Acceptance: 45.9%

#719Hard

Find K-th Smallest Pair Distance

ArrayBinary SearchSorting+1

Acceptance: 46.4%

#726Hard

Number of Atoms

Hash TableSortingStack+1

Acceptance: 65.1%

#727Hard

Minimum Window Subsequence

Dynamic ProgrammingSliding WindowString

Acceptance: 43.5%

#730Hard

Count Different Palindromic Subsequences

Dynamic ProgrammingString

Acceptance: 48.2%

#732Hard

My Calendar III

Binary SearchDesignOrdered Set+2

Acceptance: 71.9%

#736Hard

Parse Lisp Expression

Hash TableRecursionStack+1

Acceptance: 53.5%

#741Hard

Cherry Pickup

ArrayDynamic ProgrammingMatrix

Acceptance: 40.4%

#745Hard

Prefix and Suffix Search

ArrayDesignHash Table+2

Acceptance: 41.2%

#749Hard

Contain Virus

ArrayBreadth-First SearchDepth-First Search+2

Acceptance: 55.9%

#753Hard

Cracking the Safe

Depth-First SearchEulerian CircuitGraph

Acceptance: 58.5%

#757Hard

Set Intersection Size At Least Two

ArrayGreedySorting

Acceptance: 58.0%

#759Hard

Employee Free Time

ArrayHeap (Priority Queue)Sorting

Acceptance: 72.9%

#761Hard

Special Binary String

RecursionString

Acceptance: 79.4%

#765Hard

Couples Holding Hands

Breadth-First SearchDepth-First SearchGraph+2

Acceptance: 59.8%

#768Hard

Max Chunks To Make Sorted II

ArrayGreedyMonotonic Stack+2

Acceptance: 54.7%

#770Hard

Basic Calculator IV

Hash TableMathRecursion+2

Acceptance: 49.8%

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